File Checker HELP

[Capt_Ron]

I have a script that generates a filename from form elements.
I need to add some error correcting to it.

The script concatonates (spelled right?) using 3 variables from the form and 2 strings of text to form a path. I need to check the results of that against a folder to make sure the filename created actually exists before directing the browser to display the file. If the file does not exist I want a pop-up message to appear saying so and refreshing the page so the user can re-enter the request.

Here is my original script:

---------BEGIN CODE HERE--------------
<script language="javascript">
function buildLink()
{
var pdfLink
pdfLink = '../menus/'
pdfLink += document.form1.mnuMeal.value;
pdfLink += document.form1.mnuDay.value;
pdfLink += document.form1.mnuMonth.value;
pdfLink += '.pdf',

document.form1.action = pdfLink;
document.form1.submit();
}
</script>

<form name=form1>
<select name=mnuMeal>
<option value="Bre">Breakfast</option>
<option value="Lun">Lunch</option>
</select>
<select name=mnuDay>
<option value="Wek">Weekday</option>
<option value="End">Weekend</option>
</select>
<select name=mnuMonth>
<option value="Jan">Jan</option>
<option value="Feb">Feb</option>
<option value="Mar">Mar</option>
...
</select>
<input type=button value="View Menu" onclick="buildLink();">
</form>
---------END CODE HERE--------------

[glenngv]

You have to send request to the server to check if the file exists unless you have already loaded the list to javascript. But you can also do it purely client-side by using the XMLHTTP object.
Since you only need to check if the file exists, just change the line in that script:

return oxmlhttp.responseText;

to:

return (oxmlhttp.status==200) ? true:false;

which means the function returns true if the file exists and false otherwise.

And I noticed that you're accessing the value of the comboboxes using comboboxRef.value. Only few browsers support that. This is the cross-browser way:

var pdfLink = '../menus/';
var f = document.form1;
pdfLink += f.mnuMeal.options[f.mnuMeal.selectedIndex].value;
pdfLink += f.mnuDay.options[f.mnuDay.selectedIndex].value;
pdfLink += f.mnuMonth.options[f.mnuMonth.selectedIndex].value;

or better, pass the form reference to the function

function buildLink(f)
{
var pdfLink = '../menus/';
pdfLink += f.mnuMeal.options[f.mnuMeal.selectedIndex].value;
pdfLink += f.mnuDay.options[f.mnuDay.selectedIndex].value;
pdfLink += f.mnuMonth.options[f.mnuMonth.selectedIndex].value;
...
}
...
<input type="button" value="View Menu" onclick="buildLink(this.form);">

[Capt_Ron]

Glenn,

Please forgive my ignorance.
How does the page reference the XMLHTTP object? I've never used that before. (Just now learning XML)

I like the function idea. I'll make that change in the morning.

I'm real new to javascript and need a little more clarity.

Thank you very much for your time.
Ron.

[glenngv]

You don't have to know XML as the name implies. Actually, you can access any type of file (including pdf files). Just use the function from the link I posted and modify the last line as I previously said.

[Capt_Ron]

Glenn,

OK. I have the function on the page. How do I use the result?

I can now check to see if the file exists. I need to display a message if the result is false.

Thank you for your patience.

Ron.

[glenngv]

function buildLink(f)
{
  var pdfLink = '../menus/';
  pdfLink += f.mnuMeal.options[f.mnuMeal.selectedIndex].value;
  pdfLink += f.mnuDay.options[f.mnuDay.selectedIndex].value;
  pdfLink += f.mnuMonth.options[f.mnuMonth.selectedIndex].value;
  var exists = getFile(pdfLink);
  if (exists){
    location.href=pdfLink;
  }
  else alert('File "' + pdfLink + '" does not exist.');
}
...
<input type="button" value="View Menu" onclick="buildLink(this.form);">

[Capt_Ron]

Glenn,
Here is my final text. I keep getting a false on the getFile function.
Any ideas?
PS: the filename and path are correct.

---- SCRIPT ----
<script language="javascript">
function buildLink(f)
{
var pdfLink = '../menus/';
pdfLink += f.mnuLevel.options[f.mnuLevel.selectedIndex].value;
pdfLink += f.mnuMeal.options[f.mnuMeal.selectedIndex].value;
pdfLink += f.mnuMonth.options[f.mnuMonth.selectedIndex].value;
pdfLink += '.pdf';
var exists = getFile(pdfLink);
if (exists){
location.href=pdfLink;
}
else alert('Menu not available yet, please try again later."' + pdfLink);
}

function getFile(filename)
{ oxmlhttp = null;
try
{ oxmlhttp = new XMLHttpRequest();
oxmlhttp.overrideMimeType("text/xml");
}
catch(e)
{ try
{ oxmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
}
catch(e)
{ return null;
}
}
if(!oxmlhttp) return null;
try
{ oxmlhttp.open("GET",filename,false);
oxmlhttp.send(null);
}
catch(e)
{ return null;
}
return (oxmlhttp.status==200) ? true:false;
}

</script>

---- FORM SUBMIT LINE ----

<input type="button" value="View Menu" onclick="buildLink(this.form);">

[glenngv]

try putting absolute url

var pdfLink = 'http://mydomain.com/menus/';

Also try inserting alerts at some points in the function to verify values.

Can you tell me what does oxmlhttp.status return?